Modern fire fighting apparatus use a foam proportioning system (FPS) to extinguish fires with a water-foamant solution. A constant concentration of a water-foamant solution is desired for the most effective fire-extinguishing properties. Generally, the FPS can include additive pumps, which can be driven by different power sources including, for example, electric motors or hydraulic motors. For high flow rates, hydraulic motors are used due to excessive power requirements of an equivalent electric motor. The hydraulic pressure driving the hydraulic motor often varies over the period of the fire-fighting operation. As a result, hydraulic motors are less suitable for low-volume flows, because a steady stream of water-foamant solution can be difficult to provide. In addition to the hydraulic motor in the FPS, a direct current (DC) electric motor is often used to provide the low-volume flow rates.